One message left reads, "This is not suicide, this is murder." Another says, "Government of murderers."

A call for people to gather for a protest rally in Syntagma Square on Thursday afternoon is circulating on Facebook and other social media sites.

Hundreds joined together to pay their respects to Christoulas on Wednesday night at the square, which faces the parliament building and has been the scene of most of the anti-austerity rallies in recent years.

Greek citizen: The future is hopeless

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Christoulas, a 77-year-old retired pharmacist, wrote in a suicide note that the government had made it impossible for him to survive, according to Greek state TV.

His daughter, Emmy Christoulas, told CNN that her father would be cremated rather than buried, as was his wish.

The family is not planning to hold a public rally, she said, but many people continue to stop by the spot where he died, some of them lingering to discuss the worsening debt crisis.

Photographs of the makeshift memorial, accompanied by excerpts from the retiree's suicide note, dominated the front pages of Greek newspapers Thursday.

Christoulas was a member of a citizens' movement protesting austerity, called Den Plirono, or "I won't pay," a fellow member of the group told CNN.

Yiorgos Bakayiannis said he had seen Christoulas several times at protests and other civic action events.

"He came to many of our protest actions. He was a good, active citizen who cared about what was happening to the country and its citizens," Bakayiannis said.

"And his final action was obviously political. He would not have chosen such a busy spot at the busiest time of day otherwise, or left a note holding the government responsible for leaving him with no other option."

The retiree's suicide comes as the country prepares for elections that could be held as soon as May, and amid wide public anger about the austerity measures being imposed by the coalition government.

Greek Prime Minister Lucas Papademos expressed his regret Wednesday in a statement issued by his office.

"It is tragic when a fellow human being takes his own life. In those difficult times for our society we must all -- state and citizens -- support those next to us who stand in despair," he said.

Evangelos Venizelos, head of the socialist Pasok Party that holds a majority in the coalition government, called on colleagues to refrain from "political commentary" and to "show solidarity and togetherness."

Antonis Samaras, head of the conservative New Democracy Party, also part of the coalition, said politicians must do more to "help Greeks escape from despair."

According to Health Ministry data, the suicide rate jumped about 40% in the first five months of 2011, compared with a year earlier.

Greece, which is at the center of Europe's debt crisis, has struggled with an unsustainable level of debt and an economy that has been in recession for years.

Unemployment and cuts to pay, pensions and social welfare provision have caused hardship for many people.

According to Labor Ministry data, in some cases pensions have been cut by up to 40% in the past two years.

Labor Minister George Koutroumanis warned last month that pensions could be further reduced if Greece fails to recover from its five-year recession.

Speaking in parliament, he said: "If this recession continues in 2013, 2014, 2015, nobody can expect that we will have the same level of salaries and pensions."

Klimaka, a Greek nongovernmental organization that runs a suicide helpline, has said the number of people calling has doubled in the past year.

Eleni Bekiari, a psychologist working for Klimaka, said: "We have seen a big rise in calls in the suicide helpline that our NGO runs. And many of them are crisis related -- people worrying about their worsening financial situations.

"They talk to us about how they can't manage their debts, they have no money to pay bills or have lost their jobs as a result of the crisis. This is something that often pushes people to depression, which is very much linked to suicide."

Under its second bailout program, approved this year, Greece has agreed to implement a series of austerity measures and undertake broader reforms to make its economy more competitive.

Those cuts come on top of measures brought in after the first bailout in 2010.

Greece had the greatest increase in its unemployment rate of all the European Union countries last year, climbing from 14.3% in December 2010 to 21% a year later, according to figures from Eurostat, the European Union statistics office.